1. Field of the Invention
The present invention relates to a belt-driven rotary drive having a belt closed on itself which is guided over roller-shaped bodies within a pressure fluid-tight housing with the formation of movable pressure chambers, at least one of the roller-shaped bodies being connected with a rotatable shaft which is conducted out of the housing and the movable pressure chambers being adapted to be acted on by pressure fluid.
2. Description of the Related Art
A belt-driven rotary drive of this type is known from U.S. Pat. No. 4,838,148. In that case, a belt which is closed on itself is provided, with the formation of movable pressure chambers within a pressure fluid-tight housing. The pressure fluid-tight housing has within it a cylindrical hollow space in which two roller-shaped bodies are arranged alongside of each other. One of the roller-shaped bodies is stationary, i.e. non-rotatable, within the hollow space and lies completely within the kidney-shaped ring formed by the closed belt. The second roller-shaped body is rotatable around a centrally extending shaft and is connected with a shaft which extends towards the outside.
The stationary roller-shaped body is provided with two diametrically opposite openings of pressure-fluid lines, which openings, by the action of pressure-fluid, shift the belt or the pressure chambers formed in each case thereby to one side or the other, depending on which of the openings is selected. A toothing arranged on the outer circumference of the belt engages in the rotatable roller-shaped body, which is provided with a complementary toothing so that the movement of the belt is transmitted to the rotatable roller-shaped body. This rotary movement produced in this fashion can be tapped off from the shaft on the outside. In this connection, the two cylindrical bodies are so close together that a suitable sealing closure is assured between the pressure chambers produced by the closed belt.
This known rotary drive has the disadvantage that the sealing action cannot be readjusted and that, upon increased wear of the belt, the sealing action also declines.